In the pavilion of modern progressivism, no word holds a more honored place than “alternative.”

To the uninitiated, the word means a choice or option. In Progressive Land, however, devotees recognize “alternative” for what it really means: the choice of the enlightened, typically because the alternative promises some result without the aid of some evil (phosphates, in the case of alternative cleaners) — or with the help of a spiritual force thought more in tune with the harmonies of the earth (Native American or Tibetan Buddhist, in the case of alternative healing).

In this way, “alternative” becomes the preferred modifier for our progressive community. Over the years, it has spread to most every sphere of daily life, from alternative medicine, alternative farming and alternative media to alternative housing, alternative energy, alternative music and, of course, alternative lifestyles. It can even be weaponized to serve the cause of progressive justice, as those who pay the Alternative Minimum Tax well appreciate.

Yet there remains one glaring exception to the progressive embrace of all things alternative. That’s alternative public education, better known as charter schools.

We see this in New York, where a mayor who fashions himself the second coming of Fiorello La Guardia makes clear that this alternative is Public Enemy No. 1, hated even more than those enemies of the people out there trying to eke out a profit. Thus, we have Mayor de Blasio seeking to impose on charter public schools rent the traditional public schools don’t pay and depriving them of capital funding for expansion.

The mayor’s decisions on charters will have what good progressives like to call a “disparate impact” on the city’s African-American and Latino children. In the traditional public schools, four out of five of these children are failing their proficiency tests each year, and we know this gap only grows over the years. In effect, it means New York’s system of public education condemns these children to lives on the fringes of American prosperity. Charters’ record with minority achievement is far better.

It’s an odd place for progressivism to find itself. At the heart of the progressive message is the idea that the structures and institutions of the American mainstream need to be transformed if the American promise is to be made real for the nation’s poor and marginalized. Where liberals want to tweak around the edges, progressives have always favored fundamental structural change.

This the charters deliver. What could be more alternative than a public school accountable to the people it serves and not City Hall? What is more egalitarian than an admissions system based on lotteries, in contrast to private schools (based on ability to pay) or an elite public school (based on knowing a pol who can get your kid in?). And which model — the traditionals or the charters — empowers teachers and principals with the flexibility they need to innovate and teach in a way that ensures their students learn?

Looked at from this angle, Mayor Michael Bloomberg surely has the greater claim to progressive than Mayor de Blasio. Because few steps are more progressive and radical than the one he took: seeding the city with charter schools that he and his chancellor didn’t control, which would compete with the ones they did.

And this alternative produced. Not every charter is a winner, but on the whole the alternatives do better than the traditionals — the best charters are among the best schools in this city — and, in contrast to the traditionals, if they don’t get better they will go out of business.

Even Mayor de Blasio does not contest this. Nowhere does he speak about charters failing the students they serve. To the contrary, he only underscores their achievement by trying to minimize it as affecting but 5 percent of the city’s K-12 student population.

Note, too, that many charter leaders are progressives who run what they legitimately regard as alternative schools in a highly progressive manner. More power to them, so long as the kids are learning.

A progressive might see in charters the beginnings of a new structure for public education that abandons the highly centralized, top-down, one-size-fits-all system of the traditional schools in favor of a concept that offers citizens more options for their children and more accountability for those who provide them. Instead, we have a mayor who’s going to keep failing schools going so long as they are traditionals and curtail the expansion of the successful if they are alternatives.

For a man who likes to talk about New York’s “progressive future,” Bill de Blasio sure does seem awfully wed to the past.